Light-emitting device, integrated light-emitting device, and light-emitting module

ABSTRACT

A light-emitting device includes a base including a conductive wiring; a light-emitting element mounted on the base and configured to emit light; a light reflective film provided on an upper surface of the light-emitting element; and a encapsulant covering the light-emitting element and the light reflective film. A ratio (H/W) of a height (H) of the encapsulant to a width (W) of a bottom surface of the encapsulant is less than 0.5.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2015-200445, filed on Oct. 8, 2015, and Japanese Patent Application No.2016-197968, filed on Oct. 6, 2016, the disclosures of which are herebyincorporated by reference in their entirety.

BACKGROUND

The present disclosure relates to light-emitting devices, integratedlight-emitting devices, and light-emitting modules.

In recent years, various electronic components have been proposed andput into practical use, and they are required to exhibit higherperformance. In particular, some electronic components need to maintaintheir performance for a long period of time under a harsh usageenvironment. Such requirements can apply to light-emitting devices usingsemiconductor light-emitting elements, including a light-emitting diode(i.e., LED). That is, in the fields of general illumination and interiorand exterior lighting for vehicles, the light-emitting devices have beenincreasingly required day by day to demonstrate higher performance,specifically, higher output (i.e., higher luminance) and higherreliability. Furthermore, the light-emitting devices are requested to besupplied at low costs while maintaining high performance.

Backlights used in liquid crystal televisions, general lighting devices,and the like are developed by focusing on their designs, which leads toa high demand for thinning.

For example, Japanese Unexamined Patent Application Publication No.2008-4948 discloses a light-emitting device in which a reflector isprovided on the upper surface of a light-emitting element mounted on asubmount in a flip-chip manner to thereby achieve thinning of thebacklight.[

Japanese Unexamined Patent Application Publication No. 2008-4948 canachieve the light-emitting device with wide light distribution. However,with further thinning of the backlight, a light-emitting device capableof achieving much wider light distribution has been required.

SUMMARY

Embodiments of the present disclosure have been made in view of theforegoing circumstances, and it is an object of the embodiments of thepresent disclosure to provide a light-emitting device that enables widelight distribution without using a secondary lens.

A light-emitting device according to an embodiment includes: a baseincluding a conductive wiring; a light-emitting element mounted on thebase and adapted to emit light; a light reflective film provided on anupper surface of the light-emitting element; and a encapsulant coveringthe light-emitting element and the light reflective film, in which aratio (H/W) of a height (H) of the encapsulant to a width (W) a bottomsurface of the encapsulant is less than 0.5.

Accordingly, the embodiment of the present disclosure enables the widelight distribution without using a secondary lens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing an example of a light-emittingdevice according to a first embodiment.

FIG. 2 is a diagram showing incident-angle dependence of a lighttransmissivity of a light reflective film in the embodiment.

FIG. 3 is a diagram showing a relationship between a wavelength range ofa light reflective film and an emission wavelength of a light-emittingelement in the light-emitting device of the embodiment.

FIG. 4 is a light distribution characteristic diagram of thelight-emitting device in the embodiment.

FIG. 5 is a light distribution characteristic diagram of alight-emitting device using a secondary lens in Comparative Example.

FIGS. 6A-6I show Experimental Examples according to the embodiment.

FIG. 7 is a cross-sectional view showing an example of a light-emittingmodule in a second embodiment.

FIGS. 8A and 8B show an example of a light reflective plate.

FIGS. 9A and 9B show luminance distribution characteristics of alight-emitting module according to Example 2.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described below withreference to the accompanying drawings as appropriate. A light-emittingdevice to be described below is to embody the technical idea of thepresent disclosure and is not intended to limit the present inventionunless otherwise specified. The contents of the description regardingone embodiment or example can also be applied to other embodiments andexamples.

Furthermore, in the description below, the same names or referencecharacters denote the same or similar members, and thus a detaileddescription thereof will be omitted as appropriate. Moreover, regardingeach element configuring the present invention, a plurality of elementsmay be formed by the same member, thereby allowing this one member tofunction as these elements. Conversely, the function of one member canbe shared and achieved by a plurality of members.

First Embodiment

FIG. 1 is a schematic configuration diagram showing one example of alight-emitting device according to a first embodiment.

As shown in FIG. 1, in this embodiment, the light-emitting deviceincludes a base 101 with conductive wirings 102, and a light-emittingelement 105 mounted on the base 101. The light-emitting element 105 ismounted in a flip-chip manner via bonding members 103 to straddle atleast a region between a pair of conductive wirings 102 provided at thesurface of the base 101. A light reflective film 106 is formed on alight extraction surface side of the light-emitting element 105 (i.e.,upper surface of the light-emitting element 105). At least a part ofeach conductive wiring may be provided with an insulating member 104. Aregion of the upper surface of the conductive wiring 102 electricallyconnected to the light-emitting element 105 is exposed from theinsulating member 104.

The light transmissivity of the light reflective film 106 is dependenton an angle of incidence of the light incident from the light-emittingelement 105. FIG. 2 is a diagram showing incident-angle dependence ofthe light transmissivity of the light reflective film 106 in thisembodiment. The light reflective film 106 hardly allows the light topass therethrough in the direction perpendicular to the upper surface ofthe light-emitting element 105, but increases the amount of the lighttransmitted as the angle of incidence increases relative to theperpendicular direction. Specifically, when the incident angle is in arange of −30° to 30°, the light transmissivity is approximately 10%.When the incident angle becomes smaller than −30°, the lighttransmissivity gradually becomes larger. Further, when the incidentangle becomes smaller than −50°, the light transmissivity increasesdrastically. Likewise, when the incident angle becomes larger than 30°,the light transmissivity gradually becomes larger. Further, when theincident angle becomes larger than 50°, the light transmissivityincreases drastically. That is, the light transmissivity of the lightreflective film for said light increases as an absolute value of anincident angle increases. The formation of such a reflective film canachieve the batwing light distribution characteristics shown in FIG. 4.

The term “batwing light distribution characteristics” as used hereinmeans the light distribution characteristics exhibiting a first peak ina first region with a light distribution angle of less than 90°, thefirst peak having a higher intensity than that at the light distributionangle of 90°, as well as a second peak in a second region with a lightdistribution angle of more than 90°, the second peak having a higherintensity than that at the light distribution angle of 90°.

The light-emitting element 105 is covered with a light transmissiveencapsulant 108. The encapsulant 108 is disposed on the base to coverthe light-emitting element 105 in order to protect the light-emittingelement 105 from an external environment and to optically control thelight output from the light-emitting element. The encapsulant 108 isformed substantially in the dome shape. The encapsulant 108 covers thelight-emitting element 105 with the light reflective film 106 disposedthereto, the surfaces of the conductive wirings 102 located around thelight-emitting element 105, and connection portions between thelight-emitting element 105 including the bonding members 103 and theconductive wirings 102. That is, the upper surface and lateral surfacesof the light reflective film 106 are in contact with the encapsulant108, and the lateral surfaces of the light-emitting element 105 notcovered with the light reflective film 106 are also in contact with theencapsulant 108. The connection portions may be covered with anunderfill, not with the encapsulant 108. In this case, the encapsulant108 is formed to cover the upper surface of the underfill and thelight-emitting element. In this embodiment, the light-emitting element105 is directly covered with the encapsulant 108.

The encapsulant 108 is preferably formed to have a circular orellipsoidal outer shape in the top view, with the ratio of a height (H)of the encapsulant in an optical-axis direction to a diameter (width: W)of the encapsulant in the top view set to a value less than 0.5. For theencapsulant 108 having the ellipsoidal shape, there are a major axis anda minor axis that can be considered as the length of the width, but theminor axis is defined as a diameter (W) of the encapsulant 108 in thepresent specification. The upper surface of the encapsulant 108 isformed in a convex curved shape.

With this arrangement, the light emitted from the light-emitting element105 is refracted at an interface between the encapsulant 108 and air,which can achieve the wider light distribution.

Here, the height (H) of the encapsulant indicates the height from amounting surface for the light-emitting element 105 as shown in FIG. 1.The width (W) of the encapsulant indicates its diameter when theencapsulant has a circular bottom surface as mentioned above, oralternatively indicates the length of the shortest part thereof when theencapsulant has any shape other than the circle.

FIG. 4 shows an example of changes in the light distributioncharacteristics depending on the presence or absence of the encapsulant108. In FIG. 4, the solid line shows the light distributioncharacteristic of a light-emitting device 100 in the first embodiment.On the other hand, the dotted line shows the light distributioncharacteristic of a light-emitting device fabricated in the same way asin the first embodiment except that the encapsulant 108 is not formed.

As can be seen from FIG. 4 according to the light-emitting device in thefirst embodiment, the first peak moves in the direction that decreasesthe light distribution angle as well as the second peak moving in thedirection that increases the light distribution angle, as compared witha light-emitting device without the encapsulant 108. Therefore, thelight-emitting device in the first embodiment can achieve the widerlight distribution.

The use of both the light reflective film 106 and the encapsulant 108 inthis way can achieve the desired light distribution characteristicswithout using the secondary lens. That is, the formation of the lightreflective film 106 can reduce the luminance directly above thelight-emitting element 105, while the encapsulant 108 can concentrate onwidening the distribution of the light from the light-emitting element105, which enables significant downsizing of the encapsulant with a lensfunction.

In other words, conventionally, reduction in luminance directly abovethe light-emitting element while widening the light distribution ispossible only by adjusting a height of the encapsulant, as a result, theheight of the encapsulant must be increased In contrast, thelight-emitting device in this embodiment includes the light reflectivefilm 106 having reduced luminance directly above the light-emittingelement 105, thereby achieving the batwing light distributioncharacteristics. Thereby, the encapsulant 108 can be configured to focuson the function of widening the light distribution. Thus, thisembodiment can achieve downsizing of the light-emitting device.

This arrangement can achieve a thinned backlight module (i.e.,light-emitting module) with which non-uniform luminance is reduced, aswill be mentioned later. FIG. 5 shows the light distributioncharacteristics obtained by using the secondary lens as a comparativeexample. Even without using any secondary lens, the light-emittingdevice in this embodiment can achieve substantially the same lightdistribution characteristics as when using a secondary lens.

Nine light-emitting devices with different heights (H) in the opticalaxis direction of the encapsulants 108 and different diameters (widths:W) of the encapsulants in the top view were fabricated. The results oftheir light distribution characteristics are shown in FIGS. 6A-6I. Thelight-emitting element used therein was a blue LED having asubstantially square shape with one side of 600 μm in length in theplanar view and a thickness of 150 μm. The light reflective film 106formed on the main surface of the light-emitting element 105 isconfigured of eleven layers by repeatedly forming a SiO₂ layer (82 nm inthickness) and a ZrO₂ layer (54 nm in thickness).

Regarding each of the nine light-emitting devices No. 1 to No. 9, theratio of the height (H) of the encapsulant to the diameter (width: W) ofthe encapsulant is shown in Table 1.

TABLE 1 No. No. No. No. No. No. No. No. No. 1 2 3 4 5 6 7 8 9 H 0.700.89 0.92 0.79 0.93 1.09 0.74 1.00 1.18 (mm) W 2.76 2.78 2.56 3.06 3.143.11 3.40 3.28 3.29 (mm) H/W 0.25 0.32 0.36 0.26 0.30 0.35 0.22 0.300.36 Result FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. 6A 6B 6C 6D 6E6F 6G 6H 6I

As can be seen from the experimental results, the light distributioncharacteristics did not change so much due to the difference in thediameter of the encapsulant. However, the ratio of the height (H) of theencapsulant to the diameter (width: w) of the encapsulant affected thelight distribution characteristics.

The graphs of FIGS. 6A-6I show that the ratio (H/W) of the height (H) tothe width (W) of the encapsulant is preferably 0.3 or less in order toachieve a wider light distribution.

Preferred examples of the light-emitting device 100 in this embodimentwill be described below.

(Base 101)

The base 101 is a member for mounting the light-emitting element 105.The base 101 has the conductive wirings 102 on its surface to supplyelectric power to the light-emitting element 105.

Examples of a material for the base 101 can include ceramics, and resinssuch as a phenol resin, an epoxy resin, a polyimide resin, a BT resin,polyphthalamide (PPA), and polyethylene terephthalate (PET). Among them,the resin is preferably selected as the material in terms of low costand formability. The thickness of the base can be selected asappropriate. The base may be either a rigid base or a flexible basemanufacturable by a roll-to-roll system. The rigid base may be a thinnedrigid base that is bendable.

To obtain the light-emitting device with high resistance to heat andlight, ceramics are preferably selected as the material for the base101. Examples of ceramics can include alumina, mullite, forsterite,glass-ceramics, nitride-based (e.g., AlN) ceramics, and carbide-based(e.g., SiC) ceramics. Among them, ceramics made of alumina or mainlycontaining alumina are preferable.

In the use of a resin as the material for the base 101, an inorganicfiller such as glass fiber, SiO₂, TiO₂, or Al₂O₃, is mixed into theresin, thereby allowing the base to have improved mechanical strengthand improved optical reflectance, reduced thermal expansion rate, andthe like. The base 101 may be any other member as long as it canseparate and insulate a pair of conductive wirings 102 from each other.The base 101 may employ a so-called metal base that includes a metalmember with an insulating layer formed therein.

(Conductive Wiring 102)

The conductive wirings 102 are members electrically connected toelectrodes of the light-emitting element 105 and adapted to supplycurrent (electric power) from the outside to the light-emitting element.That is, the conductive wiring serves as an electrode or a part thereoffor energization with the power from the outside. Normally, theconductive wirings are formed of at least two wirings, namely, positiveand negative wirings spaced apart from each other.

Each conductive wiring 102 is formed over at least an upper surface ofthe base that serves as a mounting surface for the light-emittingelement 105. Material for the conductive wiring 102 can be selected asappropriate, depending on material used for the base 101, amanufacturing method thereof, and the like. For example, when ceramic isused as the material for the base 101, the conductive wirings 102 arepreferably made of material having a high melting point that canwithstand the sintering temperature of a ceramic sheet. Specifically,metal with a high melting point, such as tungsten or molybdenum, ispreferably used as the material for the conductive wiring. Further,other metal materials, such as nickel, gold, or silver may be formed tocover the above-mentioned surface of the conductive wiring by plating,sputtering, vapor deposition, etc.

When the glass epoxy resin is used as the material for the base 101, thematerial for the conductive wiring 102 is preferably made of materialthat is easy to process. In the case of using the epoxy resininjection-molded, the conductive wiring 102 is made of material that canbe easily processed by punching, etching, bending, etc., and has arelatively high mechanical strength. Specifically, examples of theconductive wiring can include metals, such as copper, aluminum, gold,silver, tungsten, iron, and nickel, and a metal layer or lead frame madeof an iron-nickel alloy, phosphor bronze, an iron-copper alloy,molybdenum, and the like. The surface of the lead frame may be coatedwith a metal material other than that of a lead frame main body. Suchmetal materials can be appropriately selected, for example, silveralone, or an alloy of silver and copper, gold, aluminum or rhodium.Alternatively, the conductive wiring can be formed of multiple layersusing silver or each alloy. Suitable methods for coating with a metalmaterial can include sputtering, vapor deposition, and the like as wellas the plating.

(Bonding Member 103)

The bonding members 103 are members for fixing the light-emittingelement 105 onto the base 101 or conductive wirings 102. In theflip-chip mounting, conductive members are used as the bonding membersin the same manner as in this embodiment. Specifically, suitablematerials for the bonding member can include an Au-containing alloy, anAg-containing alloy, a Pd-containing alloy, an In-containing alloy, aPb—Pd containing alloy, an Au—Ga containing alloy, an Au—Sn containingalloy, an Sn-containing alloy, an Sn—Cu containing alloy, an Sn—Cu—Agcontaining alloy, an Au—Ge containing alloy, an Au—Si containing alloy,an Al-containing alloy, a Cu—In containing alloy, and a mixture of metaland a flux.

Suitable forms of the bonding member 103 can include a liquid-type, apaste-type, and/or a solid-type (e.g., sheet-shaped, block-shaped,wire-shaped and/or powder-form). The form of the bonding member can beselected based on the composition thereof, the shape of the base, andthe like, as appropriate. These bonding members 103 may be formed of asingle member or a combination of several kinds of members.

(Insulating Member 104)

The conductive wirings 102 are preferably covered with the insulatingmember 104 except for parts thereof electrically connected to thelight-emitting element 105 and other materials. That is, as shown in therespective figures, a resist for insulating and covering the conductivewirings 102 may be disposed over the base. The insulating member 104 canfunction as such a resist.

In the case of disposing the insulating member 104, a white-based fillercan be contained in the insulating member. The white-based fillercontained in the insulating member can reduce leakage and absorption oflight, thereby enabling improvement of the light extraction efficiencyof the light-emitting device 100 as well as insulating the conductivewirings 102.

Material for the insulating member 104 can be appropriately selected onthe basis that the material is less likely to absorb the light from thelight-emitting-element and have an insulating property. Examples of thematerial for the insulating member can include epoxy, silicone, modifiedsilicone, urethane, oxetane, acrylic, polycarbonate, and polyimideresins.

(Light-Emitting Element 105)

The light-emitting element 105 mounted on the base can be one known inthe art. In this embodiment, a light-emitting diode is preferably usedas the light-emitting element 105.

A light-emitting element 105 that emits light at an appropriatewavelength can be selected. For example, a blue or green light-emittingelement can utilize ZnSe, a nitride-based semiconductor(In_(x)Al_(y)Ga_(1−x−y)N, 0≦X, 0≦Y, X+Y≦1), or GaP. A light transmissivesapphire substrate and the like can be used as a growth substrate. A redlight-emitting element can use GaAlAs, AlInGaP, etc. Moreover,semiconductor light-emitting elements made of any material other thanthe materials mentioned above can also be used. The composition,emission color, and size of the light-emitting element for use, and thenumber of light-emitting elements for use, and the like can be selectedas appropriate in accordance with the purpose.

Various emission wavelengths can be selected depending on the materialof the semiconductor layer and a mixed crystal ratio thereof. Thelight-emitting element may have positive and negative electrodes on thesame surface side to enable the flip-chip mounting, or may alternativelyhave positive and negative electrodes on its different surfaces.

The light-emitting element 105 in this embodiment has a lighttransmissive substrate, and a semiconductor layer stacked on thesubstrate. The semiconductor layer includes an n-type semiconductorlayer, an active layer, and a p-type semiconductor layer formed in thisorder. An n-type electrode is formed on the n-type semiconductor layer,and a p-type electrode is formed on a p-type semiconductor layer.

As shown in FIG. 1, the light-emitting element 105 is mounted in aflip-chip manner on the conductive wirings 102 disposed on the surfaceof the base 101 via the bonding members 103. A surface of thelight-emitting element 105 opposed to the surface thereof with theelectrodes formed thereon, that is, a main surface of the lighttransmissive substrate would serve as a light extraction surface.However, in this embodiment, the light reflective film 106 is formed onthe light extraction surface, and thus the lateral surface of thelight-emitting element 105 practically serves as the light extractionsurface. That is, part of the light emitted from the light-emittingelement 105 and directed toward the main surface of the light-emittingelement 105 is returned to the light-emitting element 105 by the lightreflective film 106, then repeatedly reflected inside the light-emittingelement 105, and eventually output from the lateral surfaces of thelight-emitting element 105. Therefore, the light distributioncharacteristics of the light-emitting device 100 (see the dotted line inFIG. 4) exhibit the characteristics of a combination of the lightpassing through the light reflective film 106 and the light emitted fromthe lateral surfaces of the light-emitting element 105.

The light-emitting element 105 is disposed to straddle the regionbetween the two conductive wirings 102 that are isolated and insulatedon positive and negative sides. The light-emitting element 105 iselectrically connected and mechanically fixed to the conductive wiringsvia the conductive bonding members 103. To mount the light-emittingelement 105, a method using bumps can be employed as well as a methodusing solder paste. As a light-emitting element 105, a small-sizedpackage product which includes the light-emitting element encapsulatedwith a resin or the like can also be used. The shape or structure of thelight-emitting element 15 can be appropriately selected.

As will be described below, in the case of the light-emitting deviceincluding a wavelength conversion member, the light-emitting elementsuitably uses a nitride semiconductor (In_(x)Al_(y)Ga_(1−x−y)N, 0≦X,0≦Y, X+Y≦1) capable of emitting light with a short wavelength that canefficiently excite a wavelength conversion layer.

Although an embodiment using flip-chip mounting has been described as anexample, certain embodiments of the present invention may employ amounting state in which an insulating base side of a light-emittingelement serves as the mounting surface, and electrodes formed on theupper surface of the light-emitting element are connected to wires. Inthis case, the upper surface of the light-emitting element is anelectrode-formed surface side, and the light reflective film ispositioned on the electrode-formed surface side.

(Light Reflective Film 106)

The light reflective film 106 is formed on the light extraction surfaceside, which is the main surface of the light-emitting element 105.

Material for the light reflective film may be one which reflects atleast the light emitted from the light-emitting element 105, forexample, metal or resin containing a white filler.

A dielectric multilayer film can be used to produce the reflective filmwith less light absorption. Additionally, the reflectance of the lightreflective film can be suitably adjusted by designing the dielectricmultilayer film, or its reflectance can also be controlled by adjustingthe angle of the light. In particular, the reflectance is increased inthe direction perpendicular to the light extraction surface (also calledthe optical axis direction), and decreased at a large angle relative tothe optical axis due to increase of the light transmissivity of thereflective film, which can control the shape of the batwing lightdistribution.

Regarding a reflection wavelength range in the optical axis direction ofthe dielectric multilayer film, i.e. in the direction perpendicular tothe upper surface of the light-emitting element, as shown in FIG. 3, itis preferable to widen a region on a long wavelength side of thereflection wavelength range, with respect to the emission peakwavelength of the light-emitting element 105.

This is because as the angle from the optical axis is varied, in otherwords, as the angle from the optical axis of the incident light isincreased, the reflection wavelength range of the dielectric multilayerfilm is shifted to the short wavelength side. By widening the reflectionwavelength range toward the long wavelength side with respect to theemission wavelength, the adequate reflectance can be maintained up to awide angle, that is, for light incident from the light-emitting elementat a large angle relative to the optical axis.

Materials suitable for use in the dielectric multilayer film can be ametal oxide film material, a metal nitride film, an oxynitride film, orthe like. Organic materials, such as a silicone resin or a fluorineresin, can also be used. However, the material for the dielectricmultilayer can be selected from ones other than those described above.

(Encapsulant 108)

Materials suitable for use in the encapsulant 108 can be lighttransmissive materials, including an epoxy resin, a silicone resin, amixed resin thereof, or glass. Among them, the silicone resin ispreferably selected by taking into consideration the resistance to lightand the formability.

The encapsulant 108 can contain: a light diffusion material, awavelength conversion material, such as phosphors or quantum dots thatabsorbs part of light from the light-emitting element 105 to outputlight with a different wavelength from that of the light emitted fromthe light-emitting element; and a colorant corresponding to the color ofemitted light from the light-emitting element.

In the case of adding these materials to the encapsulant 108, it ispreferable to use ones less likely to affect the light distributioncharacteristics. For example, the material having a particle size of 0.2μm or less is preferable because it less likely to affects the lightdistribution characteristics. The term “particle size” as used in thepresent specification means an average particle size, and the averageparticle size is measured based on a Fisher-SubSieve-Sizers-No.(F.S.S.S.No) using an air permeability method.

The encapsulant 108 can be formed by compression molding or injectionmolding to cover the light-emitting element 105. Alternatively, thematerial for the encapsulant 108 is optimized its viscosity to bedropped or drawn on the light-emitting element 105, thereby controllingthe shape of the encapsulant 108 by the surface tension of the materialitself.

In the latter formation method, a mold is not required, so that theencapsulant can be formed by a simpler method. Other than adjusting theviscosity of the base material of the encapsulant 108, the viscosity ofthe encapsulant material can be adjusted by using the above-mentionedlight diffusion material, wavelength conversion material, and/orcolorant to form the encapsulant 108 with a desired level of viscosity.

Second Embodiment

FIG. 7 is a cross-sectional view of a light-emitting module 300including a light-emitting device 200 in a second embodiment. In thisembodiment, a plurality of the light-emitting elements 105 is mounted atpredetermined intervals on the base 101. At least one light reflectivemember 110 is disposed between the adjacent light-emitting elements 105so as to reflect the light emitted at a small angle relative to theupper surface of the light-emitting element (i.e., upper surface of thebase 101). That is, the light-emitting device 200 is an integratedlight-emitting device that includes a plurality of the light-emittingdevices 100 of the first embodiment and the light reflective member 110disposed between the respective light-emitting devices 100. A lightdiffusion plate 111 for diffusing the light from the light-emittingelement 105 is disposed above the light-emitting devices 100 and thelight reflective member 110 and substantially in parallel with the uppersurfaces of the light-emitting elements. A wavelength conversion layer112 for converting part of the light emitted from the light-emittingelements 105 to light with a different wavelength is disposed above thelight diffusion plate 111 and substantially in parallel with the lightdiffusion plate 111.

In general, as the ratio of a distance between the base 101 and thelight diffusion plate 111 (hereinafter may be referred to as an opticaldistance: OD) to a distance between the adjacent light-emitting elements(hereinafter may be referred to as a pitch) is decreased, the amount oflight between the light-emitting elements 105 on the surface of thelight diffusion plate 111 becomes small, causing a dark space.

However, with the arrangement including the light reflective member 110disposed in this way, the light reflected by the light reflective member110 compensates for the amount of light between the light-emittingelements, whereby the non-uniform luminance on the surface of the lightdiffusion plate 111 can be reduced even in a region with a smaller ratioof OD/Pitch.

Specifically, in the light-emitting device 200 of the second embodiment,an inclination angle θ of a light reflective surface of the lightreflective member 110 relative to the base 101 is set such that thenon-uniform luminance on the surface of the light diffusion plate 111 isreduced taking into consideration the light distribution characteristicsof the respective light-emitting devices 100. Regarding the lightdistribution characteristics of the plurality of light-emitting devices100 arranged, each light-emitting device 100 preferably has the lightdistribution characteristics that the amount of light becomes large in aregion with a large light distribution angle, i.e., in a region at alight distribution angle of around ±90°, in order to reduce thenon-uniform luminance on the surface of the light diffusion plate 111and to achieve the thinned light-emitting device 200.

When the ratio of OD/Pitch is small, for example, 0.2 or less, anelevation angle at which the incident light enters the light reflectivemember 110 is less than 22° relative to the light-emitting surface ofthe light-emitting element 105. Thus, to increase the reflectance of thelight by the light reflective member 110 at the low OD/Pitch of 0.2 orless, the light distribution characteristics of the light-emittingdevice 100 preferably has the feature that, for example, the amount oflight at the elevation angle of less than 20° relative to the uppersurface of the base is large. Specifically, the first and second peaksof the emission intensity are preferably positioned in a range of theelevation angle of less than 20°. Here, the elevation angle of 20°corresponds to the light distribution angles of 20° and 160° in FIG. 4.In other words, the first peak of emission intensity is positioned in arange of less than 20° of the light distribution angle, and the secondpeak of emission intensity is positioned in a range of greater than 160°of the light distribution angle, as shown in FIG. 4. The amount of lightin a range of the elevation angle of less than 20° is preferably 30% ormore of the whole amount of light, and more preferably 40% or morethereof.

(Light Reflective Member 110)

The light reflective member 110 is provided between the adjacentlight-emitting elements 105.

The light reflective member may be formed of a material that reflects atleast light with the emission wavelength of the light-emitting element105. For example, a metal plate or resin containing a white filler canbe suitably used for the light reflective member.

A dielectric multilayer film can be used as a reflective surface of thelight reflective member to produce the reflective surface with lesslight absorption. Additionally, the reflectance of the light reflectivemember can be appropriately adjusted by designing the dielectricmultilayer film, or its reflectance can also be controlled by the angleof the light.

The height of the light reflective member 110 and the inclination angleθ of the light reflective surface relative to the surface of the base101 can be set to appropriate values. The reflective surface of thelight reflective member 110 may be a planar surface or a curved surface.To obtain the desired light distribution characteristics, the suitableinclination angle θ and shape of the reflective surface can be set. Theheight of the light reflective member 110 is preferably set at 0.3 timesor less and more preferably 0.2 times or less the distance between theadjacent light-emitting elements. This arrangement can provide thethinned light-emitting module 300 with less non-uniform luminance.

For the light-emitting device 200 used in an environment where the usetemperature tends to change significantly, the linear expansioncoefficient of the light reflective member 110 needs to be close to thatof the base 101. In the case where the light reflective member 110significantly differs from the base 101 in the linear expansioncoefficient, warpage might occur in the light-emitting device 200 due tothe change in temperature, or otherwise the positional relationshipbetween the components, especially, between the light-emitting device100 and the light reflective member 110 might shift, thus possiblyfailing to obtain the desired optical properties. However, the linearexpansion coefficient is a physical property and thus there are not somany alternatives in reality. For this reason, the light reflectivemember 110 is preferably formed by a film molded component that iselastically deformable in order to reducing the occurrence of warpage ofthe light-emitting device 200 even in the case where the lightreflective member significantly differs from the base in the linearexpansion coefficient. This is because the light reflective member 110made of a less elastically deformable material, such as solid materialtends to expand while maintaining its shape, but the film-shaped lightreflective member can be appropriately deformed to compensate itsexpansion.

Preferably, a plurality of the light reflective members 110 is coupledtogether into a plate shape to have through holes 113 where thelight-emitting devices 200 are disposed. FIG. 8 shows such aplate-shaped light reflective plate 110′. FIG. 8A is a top view of thelight reflective plate 110′, and FIG. 8B is a cross-sectional view takenalong the line A-A of FIG. 8A. Such a light reflective plate 110′ can beformed by metal molding, vacuum forming, pressure molding, pressforming, and the like. The light reflective plate 110′ is disposed onthe base 101. The light reflective member 110 may be formed by a methodwhich involves drawing a light reflective resin directly on the base101, and the like. The height of the light reflective member 110 ispreferably set at 0.3 times or less the distance between the adjacentlight-emitting elements, and for example, more preferably 0.2 times orless the distance between the adjacent light-emitting elements.

Example 1

In this example, as shown in FIG. 1, a glass-epoxy-based material isused for the base 101, and a Cu material of 35 μm in thickness is usedas the conductive wiring.

A nitride-based blue LED may be used as the light-emitting element 105.The LED has an approximately square shape with one side of 600 μm inlength in the planar view and a thickness of 150 μm. An epoxy-basedwhite solder resist may be used as the insulating member 104.

The light reflective film 106 formed on the main surface of thelight-emitting element 105 is configured of eleven layers by repeatedlyforming a SiO₂ layer (82 nm in thickness) and a ZrO₂ layer (54 nm inthickness).

At this time, the light transmissivity of the light reflective film 106is shown in FIG. 2. The light transmissivity in the directionperpendicular to the main surface side of the light-emitting element(i.e., in the optical axis direction) is low, and the lighttransmissivity of the light reflective film is increased as an angleaway from the optical axis increases.

The light-emitting element 105 is covered with the encapsulant 108. Theencapsulant 108 is formed of a silicone resin and has a height (H) of1.0 mm and a diameter of the bottom surface (W) of 3.0 mm.

With this arrangement, the light emitted from the light-emitting element105 is refracted at an interface between the encapsulant 108 and air,which widens the range of the light distribution angles. The lightdistribution characteristic of the light-emitting device 100 obtained bythis arrangement is indicated by the solid line in FIG. 4. The lightdistribution characteristic obtained by a light-emitting device withoutthe encapsulant 108 is indicated by the dotted line in FIG. 4. In thisway, the encapsulant 108 is used together with the light reflective film106, which can achieve the lower OD/Pitch.

Example 2

In Example 2, a plurality of light-emitting elements 105 of Example 1are mounted on the base 101, and the at least one light reflectivemember 110 is disposed between the adjacent light-emitting elements.Here, Pitch is set at 12.5 mm.

The light reflective member 110 is a plate-shaped light reflectiveplate, which is formed using a polypropylene sheet containing a TiO₂filler (having a thickness (t) of 0.2 mm) by the vacuum forming methodso as to have a reflection angle θ (i.e., elevation angle) of 55° and aheight of 2.4 mm. The light reflective member 110 is a plate-shapedlight reflective plate shown in FIG. 8 and disposed on the insulatingmember 104.

Over the light reflective member 110, a milky-white light diffusionplate 111 and a wavelength conversion layer 112 are disposed to form aliquid crystal backlight (i.e., light-emitting module). In thisarrangement, FIGS. 9A and 9B show the result of comparison of thenon-uniform luminance on the surface of the light diffusion plate 111between the presence and absence of the light reflective member 110.FIG. 9A shows a light-emitting module without light reflective member,and FIG. 9B shows a light-emitting module in the presence of the lightreflective member. As shown in FIGS. 9A and 9B, in the case where thelight reflective member is not disposed, the relative luminance isdecreased to in a range of about 0.6 to about 0.7 within a region wherethe relative luminance tended to be high (i.e., in a range of the numberof pixels between about 250 pixels to about 720 pixels). On the otherhand, in the case where the light reflective member is disposed, therelative luminance is not decreased to below about 0.8 within the regionwhere the relatively luminance tended to be high (i.e., at the number ofpixels between about 250 pixels to about 720 pixels). In other words, itcan be seen the effect that non-uniform luminance is improved byproviding the light reflective member.

The light-emitting device and light-emitting module of the presentembodiments can be used in backlight light sources for liquid crystaldisplays, various lighting fixtures, and the like.

What is claimed is:
 1. A light-emitting device comprising: a baseincluding a conductive wiring; a light-emitting element mounted on thebase and configured to emit light; a light reflective film provided onan upper surface of the light-emitting element; and a encapsulantcovering the light-emitting element and the light reflective film,wherein a ratio (H/W) of a height (H) of the encapsulant to a width (W)of a bottom surface of the encapsulant is less than 0.5.
 2. Thelight-emitting device according to claim 1, wherein the encapsulant hasan upper surface with a convex curved shape.
 3. The light-emittingdevice according to claim 1, wherein the light reflective film isconfigured such that a light transmissivity of the light reflective filmfor said light has incident-angle dependence.
 4. The light-emittingdevice according to claim 1, wherein a light transmissivity of the lightreflective film for said light increases as an absolute value of anincident angle of said light increases.
 5. The light-emitting deviceaccording to claim 1, wherein the light reflective film is formed of adielectric multilayer film.
 6. The light-emitting device according toclaim 1, wherein: a reflection wavelength range of the light reflectivefilm for light perpendicularly incident on the light reflective filmincludes an emission peak wavelength of the light-emitting element, andin the reflection wavelength range, a region on a longer wavelength sideof the emission peak wavelength is wider than a region on a shorterwavelength side of the emission peak wavelength.
 7. The light-emittingdevice according to claim 1, wherein 30% or more of total light emittedfrom the light-emitting device is emitted in a direction at an elevationangle of less than 20° relative to an upper surface of the base.
 8. Thelight-emitting device according to claim 1, wherein 40% or more of totallight emitted from the light-emitting device is emitted in a directionat an elevation angle of less than 20° relative to an upper surface ofthe base.
 9. The light-emitting device according to claim 1, wherein theratio (H/W) of a height (H) of the encapsulant to a width (W) of thebottom surface of the encapsulant is 0.3 or less.
 10. The light-emittingdevice according to claim 1, wherein the light-emitting element ismounted in a flip-chip manner.
 11. An integrated light-emitting devicecomprising: a plurality of the light-emitting devices according to claim1, wherein at least one light reflective member is disposed betweenadjacent ones of the light-emitting devices.
 12. The integratedlight-emitting device according to claim 11, wherein the lightreflective member has a height that is 0.3 times or less than a distancebetween the adjacent light-emitting devices.
 13. The integratedlight-emitting device according to claim 11, wherein the lightreflective member has a height 0.2 times or less a distance between theadjacent light-emitting devices.
 14. A light-emitting module comprising:the light-emitting device according to claim 1; and a wavelengthconversion member located at a light extraction surface side of thelight-emitting device, the wave length conversion member beingconfigured to absorb part of the light emitted from the light-emittingelement and to convert the absorbed light to light with a wavelengthdifferent from an emission wavelength of the light-emitting element. 15.A light-emitting module comprising: the integrated light-emitting deviceaccording claim 11; and a wavelength conversion member located at alight extraction surface side of the integrated light-emitting device,the wavelength conversion member being configured to absorb part oflight from the light-emitting element and to convert absorbed light tolight with a wavelength different from an emission wavelength of thelight-emitting element.